In U.S. Pat. No. 4,248,160, a hatch cover and strap assembly is disclosed in which the strap and hatch cover are both pivotably mounted about a common pivot axis on a railway car roof. The strap engages the cover at the mid-portion of the cover and at the distal end of the strap, on the lower surface of the cover. An overcenter latch assembly is pivotably mounted upon the car roof at a location opposite the common hatch cover and strap pivot axis. This latch assembly includes a bifurcated overcenter locking handle which has a pair of cam surfaces which in closed position engage spaced wear plate surfaces located on the strap.
An operating handle for the latch assembly in closed position extends from the cam surfaces toward the strap and hatch cover pivot axis.
However, when the car is under pressure above atmospheric, it has been found that when the operating handle is manually pivoted outwardly from the overcenter position toward open position, and out of engagement with the strap, the pressure in the car acting on the cover and the strap causes the cover and strap to fly up, creating a hazard for the attendant.